Accessing a view controller created through Storyb

问题:

I'm working on an iOS5 app using storyboard, and I have a method in a view controller class that i'd like to access from the App Delegate. The trouble is, this view controller gets instantiated via a tab bar controller in storyboard, so the App Delegate has no direct way of calling the method I want...

For a view controller to get in touch with the App Delegate, all one has to do is use:

MyAppDelegate *appDelegate = (MyAppDelegate *)[[UIApplication sharedApplication] delegate];

Is there a similarly easy way of pointing to an already-instantiated view controller or class?

回答1:

You'll have to traverse the view hierarchy from the app delegate. Assuming the AppDelegate holds a reference to the UITabBarController, you could use the viewControllers property or selectedViewController property to get to your view controller.

回答2:

Thanks to Jerry (above), here's the code that got me what I wanted:

    UINavigationController *navigationController = (UINavigationController *)self.window.rootViewController;
MasterViewController *result;

//check to see if navbar "get" worked
if (navigationController.viewControllers) 

    //look for the nav controller in tab bar views 
    for (UINavigationController *view in navigationController.viewControllers) {

        //when found, do the same thing to find the MasterViewController under the nav controller
        if ([view isKindOfClass:[UINavigationController class]])
            for (UIViewController *view2 in view.viewControllers) 
                if ([view2 isKindOfClass:[MasterViewController class]])                    
                    result = (MasterViewController *) view2;
}

回答3:

I probably would do it in reverse. Create a method in AppDelegate call registerViewController or something. In every ViewController, call the method with itself with a name. Then in AppDelegate, you can do whatever you want afterward. It is messy to do all sort of drill

In AppDelegate

- (void)registerViewController:(NSString *)name controller:(UIViewController *)controller
{
    if(_viewControllers == nil)
    {
        _viewControllers = [[NSMutableDictionary alloc] init];

    }

    [_viewControllers setObject:controller forKey:name];
}

In any ViewController

- (void)viewDidLoad
{
    [super viewDidLoad];

    AppDelegate *appDelegate = [[UIApplication sharedApplication] delegate];
    [appDelegate registerViewController:@"feelings" controller:self];
}

In AppDelegate

XViewController *vc = (XViewController *)[_viewControllers objectForKey:@"X"];
[X startSpinner];

Hope this help

BS

回答4:

If you are using a storyboard, and you want instance of a viewController in storyboard you can use the following

UIStoryboard *mystoryboard = [UIStoryboard storyboardWithName:@"Main" bundle:nil];
id viewcontroller = [mystoryboard instantiateViewControllerWithIdentifier:@"identifier"];

Here the 'identifier' is the name provided in the particular viewController's 'storyBoard ID' in 'Identity' section in 'Identity Inspector'.

回答5:

I have a better solution. You can use window.rootViewController.storyboard to get a reference to the storyboard of that view.

回答6:

In the AppDelegate, you could simply use indexes to access the controllers via UITabBarController:

UITabBarController *tabBarController = (UITabBarController *)self.window.rootViewController;
firstViewController = [[tabBarController viewControllers] objectAtIndex:0];
secondViewController = [[tabBarController viewControllers] objectAtIndex:1];
thirdViewController = [[tabBarController viewControllers] objectAtIndex:2];

Naturally, this will get messed up if you change the ordering of the tab bar. Also, if you're looking for a controller deeper in the hierarchy, you need to do a bit more legwork.

回答7:

Swift

This is the Swift version of @infiniteLoop's answer.

let storyboard = UIStoryboard(name: "Main", bundle: nil)
let myViewController = storyboard.instantiateViewControllerWithIdentifier("identifier") as! MyViewController

You need to replace the storyboard name, view controller name, and view controller identifier with whatever you used in your project.

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